Answer
Magnets a. and c. create the dipole shown.
Work Step by Step
Magnetic field lines are continuous--the south pole and north pole are connected by field lines. Inside of a magnetic dipole, the field lines go from South to North, but externally, the loop around from North to South.
That being said, in the given picture, the field lines go from left to right INSIDE the magnetic dipole (the gray surface with the arrows), so this means that the left side is the south pole and the right side is the north pole.
The magnets needed to induce this pole must have opposite poles at the end of the magnet closest to the magnetic dipole to that of the magnetic dipole on its side.
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The left side of the magnetic dipole is the south pole, as discussed earlier, which means that the magnet that induces the shown magnetic field must have a north pole close to the dipole. This would be answer choice a.
The right side of the magnetic dipole is the north pole, which means that the magnet that induces it must have a south pole close to the dipole. This would be answer choice c.
Magnets a. and c. create the dipole shown.
